Frequently the entrance is a weak spot in the insulation of the cellar,
and it is useless to protect the roof and sides unless care is used in
the building of the entrance. If the entrance is at the end or one side
of the cellar, it will be necessary to build a sort of vestibule with
double doors so that the heat of the cellar will not be lost rapidly.
The heavier and thicker these doors, the better for the bees.
The best type of vestibule is a long, narrow passage lending into the
hillside, and it should be closed by doors at both the inside and
outside ends. If possible the vestibule should be built and protected
so that the temperature within the vestibule will never fall below
freezing. In the building of the vestibule, also, the beekeeper should
consider the ease with which the bees may be carried in and out of the
cellar.